1. Field of the Invention
The present invention relates to a reaction and separating filtration apparatus and to a method using such an apparatus. In particular, the present invention relates to an apparatus and method in which a desired product can be distinguished and collected using a permeable membrane or a filtration membrane while oscillation stirring.
2. Description of the Related Art
As a filtration apparatus for performing ultrafiltration (UF) or reverse osmosis filtration (RO), an apparatus proposed by the present inventor is known (refer to Japanese Patent Application No. Hei 10-262225) which has the structure shown in FIGS. 31, 32(A), and 32(B). In such a filtration apparatus, a pair of impermeable spacer members 3 are provided at both end sections of a pair of supports 1a and 1b which are constructed from an impermeable member so that the spacer members are pinched in between. A membrane-type filtration medium 4 is provided in the space defined by these impermeable members. The sample to be filtered (filtration object) is introduced into the space surrounded by the filtration medium, and by applying a pressure to the space or by reducing the external pressure via the filtration medium, the filtration object is permeated through the filtration medium 4 and the filtrate is taken out from an outlet 5.
Moreover, filtration medium 4 is also provided respectively along the inner walls of the supports 1a and 1b, and a stirrer 2 is provided in parallel with the two filtration media. The stirrer 2 comprises a stirring axis 2a and ladder 2b mounted on the stirring axis 2a. When the stirrer oscillates in the vertical direction between the filtration media 4, formation of a boundary film and a cake layer near the inner wall of the filtration media 4 is inhibited, and, thus, reduction in filtration efficiency can be prevented.
When the target to be isolated within the original fluid is transported near the membrane by the permeation flux at the membrane and blocked by the membrane, it accumulates near the membrane surface, resulting in an increase in the relative concentration at the membrane surface with respect to the concentration within the original fluid itself (this phenomenon is known as a concentration polarization) and formation of a “boundary film” at the membrane surface. Because the filtration resistance is increased by the boundary film, it is known that the filtration efficiency is generally reduced.
The “cake layer” mentioned above is a layer formed from the deposition of particulate materials or powdery materials near the membrane surface, for example, when the particulate or powdery materials are filtered by the membrane from a solution with the particulate or powdery materials dispersed.
As shown in FIGS. 32(A) and 32(B), the ladder 2b of the stirrer 2 is constructed by vertically providing a plurality of stirring blades 2c on the stirring axis 2a with a predetermined space in between. The stirrer 2 is also configured to oscillate with respect to the filtration medium 4. A cut section 2d is provided on a stirring blade 2c, and gaps C in which the filtration object can be circulated is formed alternately at the right and left sides, between the stirring blades 2c and the inner walls 3a of the spacer member 3. The filtration object is circulated through the flow path so that stagnation does not occur, and generation of the boundary films and cake layers can be inhibited. Furthermore, strengthening axes 2e are provided so that the plurality of stirring blades 2c moves as one unit.
In the above filtration apparatus, filtration is performed while the formation of the boundary film and the cake layer is inhibited by circulating the filtration object alternately in the right and left sides within the space.
However, the characteristics of the permeating materials and filtration objects differ according to their types, and, thus, there is a need to change the method of circulating the filtration objects according to their characteristics in order to efficiently inhibit formation of the boundary film and cake layer.